UNIVERSITY  OF  CALIFORNIA  Agricultural  Experiment  Station 

College  of  Agriculture  e.  w.  hilgard,  director 

BERKELEY,  CALIFORNIA 


CIRCULAR  No.  2. 

(May,  1903.) 


BLACKLEG 

By  ARCHIBALD  R.   WARD, 
Veterinarian  and  Bacteriologist. 


Synonyms. — Blackleg  is  also  known  as  Symptomatic  Anthrax,  Em- 
physematous Anthrax,  Quarter  111,  Black  Quarter,  and  Rauschbrand. 

Animals  Affected. — For  all  practical  purposes  the  disease  may  be  con- 
sidered as  merely  one  of  cattle,  occurring  chiefly  among  young  stock 
between  the  ages  of  three  months  and  four  years.  Cattle  under  three 
months  are  naturally  immune,  and  for  the  same  reason  animals  over 
four  years  but  rarely  are  attacked.  It  is  a  matter  of  common  observa- 
tion that  calves  in  good  condition  are  more  liable  to  attack  than  poorer 
ones.  Nevertheless,  it  is  not  safe  to  consider  that  poor  condition  will 
confer  immunity  against  blackleg.  The  disease  is  not  communicable 
to  man. 

Symptoms. — The  most  important  symptom  is  the  occurrence  of  swell- 
ings under  the  skin  on  any  part  of  the  body  except  on  the  legs  below 
the  knees  or  hocks.  The  swellings  when  first  appearing  are  painful,  but 
as  they  become  larger  the  skin  in  the  center  of  the  swelling  becomes 
insensible.  The  enlargements  are,  to  a  large  extent,  composed  of  gas 
bubbles  imprisoned  in  the  loose  tissues  beneath  the  skin,  and  the  large 
ones,  when  pressed,  give  forth  a  very  characteristic  crackling  sound. 
When  a  swelling  is  tapped  with  the  finger,  it  emits  a  drum-like  resonance. 
When  occurring  upon  the  legs,  the  tumors  may  cause  lameness  and 
even  prevent  the  victim  from  walking  at  all.  If  the  tumor  is  cut  open, 
black  or  frothy  blood  runs  out.  Fever  is  present  and  is  manifested  by 
the  usual  indications,  such  as  quickened  breathing,  dullness,  and  loss 
of  appetite.  Death  occurs  within  a  period  varying  from  eight  hours  to 
two  days  after  the  beginning  of  the  attack. 

Changes  Observed  After  Death. — The  carcass  bloats  rapidly  and  like 
wise  decomposes  quickly  after  death.  When  swellings  are  cut  open  they 
are  found  to  contain  more  or  less  clotted  black  blood  and  gas.     The 


—    2    — 

excessive  blackening  by  blood  gives  rise  to  the  various  names,  such  as 
black  quarter  and  blackleg.  Some  internal  organs  are  more  or  less 
affected,  but  the  changes  in  the  internal  organs  need  not  be  considered 
in  recognizing  the  disease. 

Cause. — The  disease  is  brought  about  by  bacteria  which  live  naturally 
in  the  soil  and  which  gain  access  to  the  body  through  wounds,  and  more 
rarely  with  food  eaten.  The  germs  of  blackleg  are  quite  generally  dis- 
tributed, but  certain  soils  have  been  observed  to  offer  particularly 
favorable  conditions  for  their  existence,  and  in  consequence  are  especially 
dangerous  for  stock  pastured  thereon.  Among  these  are  damp  or  water- 
logged soils,  or  heavy  clay  soils.  Punctured  wounds,  such  as  those 
produced  by  barbed  wire,  briers,  stubble,  etc.,  are  regarded  as  fruitful 
sources  of  infection.  A  diseased  animal  is  not  regarded  as  a  direct 
source  of  danger  to  other  animals  in  contact  with  it.  If  the  swellings 
have  been  cut  open  and  blood  is  discharged,  there  is  more  danger. 

Disposal  of  the  Dead. — Burning  is  preferable  to  any  other  method  of 
disposal,  as  it  is  the  only  means  that  can  be  relied  upon  to  absolutely 
destroy  all  germs  of  the  disease  with  which  the  carcass  is  teeming. 
When  the  victim  is  buried  the  germs  will  remain  alive  in  the  soil  long 
after  the  carcass  has  decomposed,  and  will  constitute  a  menace  to  the 
health  of  stock  pastured  upon  the  land.  Earthworms  are  said  to 
convey  infection  to  the  surface. 

Treatment  Useless. — No  successful  treatment  is  known,  and  even  should 
a  remedy  be  discovered,  its  usefulness  would  be  limited,  owing  to  the 
rapidly  fatal  nature  of  the  affection.  Cutting  open  the  swellings  and 
injecting  various  medicines  has  seldom  met  with  success.  Excessive 
exercise  and  bleeding  have  also  been  found  next  to  useless. 

Prevention  by  Vaccination. — The  method  is  based  upon  the  principle 
that  an  attack  of  the  disease  may  be  warded  off  by  purposely  causing 
the  animal  to  have  an  exceedingly  mild  attack  by  artificial  means. 
Vaccine  is  prepared  by  obtaining  flesh  from  a  diseased  animal,  finely 
dividing  it  and  subjecting  it  to  a  high  temperature  for  several  hours. 
This  treatment  of  the  diseased  material  reduces  the  disease-producing 
power  of  the  blackleg  germs  that  it  contains.  The  vaccine  material, 
when  injected  under  the  hide  of  a  healthy  calf,  produces  little  or  no 
visible  effect  upon  the  health,  but  experience  shows  that  this  vaccina- 
tion protects  the  animal  from  catching  the  disease  naturally  for  a  year 
or  more.  The  method  was  originated  in  Europe  in  1883,  and  has  since 
been  improved  upon  and  used  in  all  districts  of  the  civilized  world 
where  stock-raising  is  carried  on  extensively.  Vaccination  as  a  pre- 
ventive of  blackleg  has  been  and  is  encouraged  by  the  Bureau  of 
Animal  Industry  of  the  United  States  Department  of  Agriculture  and 


—  3  — 

the  Agricultural  Experiment  Stations  in  the  various  States.     Its  use  has 
long  since  passed  the  uncertain  experimental  stage. 

When  Not  to  Vaccinate. — Calves  should  not  be  vaccinated  unless  it  is 
known  that  the  disease  has  previously  occurred  among  animals  pastured 
on  the  same  land.  When  vaccination  is  practiced  there  is  great  risk  of 
introducing  the  germs  of  the  disease  and  thus  infecting  the  land,  which 
would  necessitate  vaccinating  annually  thereafter.  A  stock  owner  can 
much  better  afford  to  ascertain  that  his  range  is  infected  by  waiting 
until  a  death  has  occurred,  than  to  rush  into  vaccinating  before  he  is 
certain  that  it  is  necessary.  Blackleg  does  not  sweep  over  a  region  rapidly 
like  some  infectious  diseases.  Do  not  castrate  or  dehorn  at  the  time 
of  vaccination.  Do  not  vaccinate  animals  already  stricken  with  the 
disease.  ' 

What  Animals  to  Vaccinate. — Animals  between  the  ages  of  five  months 
and  two  years  should  be  vaccinated  several  weeks  before  the  disease 
usually  appears.  Animals  older  or  younger  occasionally  die  of  the 
disease,  but  it  is  not  profitable  to  vaccinate  against  these  attacks,  for  they 
occur  rarely.  If  animals  under  six  months  are  vaccinated,  the  process 
should  be  repeated  the  following  year.  The  operation  is  facilitated  by 
confining  the  calves  in  a  chute. 

Where  Vaccine  May  Be  Obtained. — The  Bureau  of  Animal  Industry, 
United  States  Department  of  Agriculture,  Washington,  D.  C,  furnishes 
vaccine  free  to  all  applicants.  Each  stock  owner  must  apply  directly 
to  Dr.  D.  E.  Salmon,  the  Chief  of  the  Bureau  of  Animal  Industry,  and 
an  application  blank  will  be  mailed  to  him,  upon  which  the  owner  shall 
indicate  the  amount  needed,  etc.  Under  no  circumstances  will  blackleg 
vaccine  be  sent  to  any  one  person  for  distribution  to  others,  or  for  use 
upon  other  cattle  than  his  own.  For  administering  the  vaccine,  a  vac- 
cinating outfit  must  be  obtained,  costing  from  $4  to  $6.  The  outfit  can 
usually  be  readily  obtained  through  drug  stores.  Vaccine  prepared  by 
private  firms  can  be  purchased  from  the  druggist  or  directly  from  the 
addresses  below.  Firms  preparing  vaccine,  known  to  the  writer,  are: 
The  H.  K.  Mulford  Co.,  represented  by  Thomas  G.  Finley,  41  Stevenson 
street,  San  Francisco;  The  Cutter  Analytic  Laboratory,  Rialto  Build- 
ing, San  Francisco;  The  Pasteur  Vaccine  Co.,  represented  by  Cadogan 
&  McClure,  110  Jessie  street,  San  Francisco;  Parke,  Davis  Co.,  Detroit, 
Michigan.  The  various  manufacturers  supply  vaccinating  outfits  and 
furnish  plainly  worded  directions  for  use. 


